Analysis of aluminum alloys with X-ray fluorescence

Aluminum is a versatile material widely used by many manufacturers, who purchase large quantities of it in the form of rods or sheets: so-called semi-finished goods. Before being warehoused or processed, these intermediate products must be checked for their exact alloy composition, because not every alloy is suitable for every application. Many different aluminum alloys are available, each with distinct properties. Employing a non-destructive but precise material analysis method during incoming goods inspection ensures that the alloy’s components are found in the correct concentrations – and that the received goods can indeed be utilized for the intended purpose.

The properties of aluminum alloys can be greatly modified by adding different constituents. For example, adding copper increases strength, but the resulting alloy cannot be welded; on the other hand, manganese lends good plasticity and corrosion properties. Magnesium, silicon, zinc and many other alloy constituents are also used to modify hardness, strength and ductility, to protect against corrosion and the effects of temperature, and to control thermal and electrical conductivity. Furthermore, the constituents influence the processing properties of the alloys: while some can only be welded in an argon environment, others cannot be machined or shaped, but might be suitable for casting.

Fig.1: Aluminum rods

This means that an incoming goods inspection at e.g. an automotive supplier must verify that the alloy contains no copper, because of its negative effect on corrosion and welding properties. Since even small amounts of an additive can substantially influence the properties of an alloy, the material analysis must be very precise and accurate. The X-ray fluorescence devices from FISCHER consistently meet this demand, and more.

Al(%)

Mg(%)

Si(%)

Ti(%)

Cr(%)

Mn(%)

Sample 1

96.61

2.459

0.000

0.033

0.018

0.150

s

0.112

0.103

0.020

0.003

0.002

0.002

Sample 2

99.00

0.339

0.290

0.024

0.001

0.023

s

0.079

0.058

0.047

0.003

0.000

0.001

Sample 3

96.20

2.896

0.000

0.033

0.017

0.150

s

0.104

0.092

0.029

0.003

0.001

0.002

Sample 4

96.36

2.711

0.004

0.033

0.017

0.150

s

0.061

0.057

0.029

0.003

0.001

0.002

Fe(%)

Ni(%)

Cu(%)

Zn(%)

Sn(%)

Pb(%)

Sample 1

0.428

0.027

0.050

0.095

0.015

0.015

S

0.004

0.001

0.001

0.000

0.001

0.001

Sample 2

0.184

0.026

0.001

0.002

0.010

0.002

S

0.002

0.000

0.000

0.000

0.002

0.000

Sample 3

0.432

0.027

0.051

0.094

0.014

0.015

S

0.004

0.001

0.001

0.000

0.001

0.000

Sample 4

0.418

0.027

0.050

0.094

0.015

0.015

s

0.003

0.000

0.001

0.001

0.001

0.000

Tab.1: Four samples were analysed. Sample 2 can clearly be distinguished from Samples 1, 3, and 4. For most elements, even small traces in the range of 100 ppm can be detected.

A complication in analyzing aluminum is that the fluorescence radiation of lightweight elements like magnesium, aluminum and silicon are absorbed in air. The solution is the FISCHERSCOPE® X-RAY XUV® 773, which works in a vacuum chamber. Furthermore, via the instrument’s WinFTM® software, it is possible to program multiple measurement settings within a single measurement cycle. For example, in order to accurately detect the lighter elements, a different setting is needed than for heavier elements. Using the so-called multiple excitation measurement mode, WinFTM® can collect the information that would be gained with both settings and analyse all alloy constituents in a single measurement.

The FISCHERSCOPE® X-RAY XUV® 773 can be used for precise and reliable materials analyses of aluminum alloys, helping to safeguard against slight deviations in the alloy composition that might render the material unusable.For more information, please contact your local FISCHER representative.